In U.S. Pat. No. 4,582,815, issued Apr. 15, 1986, is disclosed a method for the preparation of a silica extrudate whereby a particulate silica is mixed with water and an alkali metal compound to prepare a mixture which is extruded. However, the use of an alkali metal makes it necessary that the extruded silica must be soaked in a solution of ammonium nitrate and nitric acid to remove the alkali metal. The same applies to silicas containing another refractory oxide, such as alumina, according to the above-mentioned U.S. Pat. No. 4,582,815.
Applicant has found that this purification process may be obviated by using an alkanolamine or ammonia in the preparation of a dough from which silica-alumina extrudates can be obtained.